[v6,1/1] <sys/tagged-address.h>: An API for tagged address

diff --git a/NEWS b/NEWS
index 79c895e382..4f80340f9f 100644
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,7 @@  Version 2.35
 
 Major new features:
 
-  [Add new features here]
+* Add <sys/tagged-address.h> to provide an API for tagged address.
 
 Deprecated and removed features, and other changes affecting compatibility:
 
diff --git a/bits/tagged-address-mask.h b/bits/tagged-address-mask.h
new file mode 100644
index 0000000000..8762921083
--- /dev/null
+++ b/bits/tagged-address-mask.h
@@ -0,0 +1,47 @@ 
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_TAGGED_ADDRESS_MASK_H
+#define _BITS_TAGGED_ADDRESS_MASK_H 1
+
+#ifndef _SYS_TAGGED_ADDRESS_H
+# error "Never include this file directly.  Use <sys/tagged-address.h> instead"
+#endif
+
+#include <bits/tagged-address-valid-bits.h>
+
+#ifdef __cplusplus
+# if __cplusplus >= 201103L
+#  define TRANSLATED_ADDRESS_ASSERT static_assert
+# else
+#  define TRANSLATED_ADDRESS_ASSERT(expr, msg)
+# endif
+#else
+# define TRANSLATED_ADDRESS_ASSERT _Static_assert
+#endif
+
+/* A mask for constant address BITS used in address translation.  */
+#define TRANSLATED_ADDRESS_MASK(BITS)			\
+  (__extension__					\
+    ({							\
+       TRANSLATED_ADDRESS_ASSERT			\
+         (TRANSLATED_ADDRESS_VALID_BITS (BITS),		\
+	  "Translated address bits must be valid");	\
+       (((uintptr_t) 1) << (BITS)) - 1;			\
+     }))
+
+#endif /* <bits/tagged-address-mask.h> */
diff --git a/bits/tagged-address-valid-bits.h b/bits/tagged-address-valid-bits.h
new file mode 100644
index 0000000000..995bc2899b
--- /dev/null
+++ b/bits/tagged-address-valid-bits.h
@@ -0,0 +1,28 @@ 
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_TAGGED_ADDRESS_VALID_BITS_H
+#define _BITS_TAGGED_ADDRESS_VALID_BITS_H 1
+
+#ifndef _SYS_TAGGED_ADDRESS_H
+# error "Never include this file directly.  Use <sys/tagged-address.h> instead"
+#endif
+
+/* Non-zero if constant address BITS is a valid translated address bits.  */
+#define TRANSLATED_ADDRESS_VALID_BITS(BITS) 0
+
+#endif /* <bits/tagged-address-valid-bits.h> */
diff --git a/csu/libc-start.c b/csu/libc-start.c
index 0350b006fd..6f8ffa08f0 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -402,6 +402,9 @@  LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
     GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
 #endif
 
+  /* set_translated_address_mask can only be called before main.  */
+  GL(dl_translated_address_mask_locked) = 1;
+
 #ifndef SHARED
   _dl_debug_initialize (0, LM_ID_BASE);
 #endif
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 0155718175..028db5be37 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -213,6 +213,11 @@  struct link_map *_dl_sysinfo_map;
 
 # include "get-dynamic-info.h"
 #endif
+
+/* If nonzero, the mask for address bits used in address translation
+   is locked.  */
+int _dl_translated_address_mask_locked;
+
 #include "setup-vdso.h"
 /* Define the vDSO function pointers.  */
 #include <dl-vdso-setup.c>
diff --git a/include/sys/tagged-address.h b/include/sys/tagged-address.h
new file mode 100644
index 0000000000..a216814655
--- /dev/null
+++ b/include/sys/tagged-address.h
@@ -0,0 +1,18 @@ 
+#include <misc/sys/tagged-address.h>
+
+#ifdef _ISOMAC
+/* Get the current address bits used in address translation.  */
+extern unsigned int __libc_get_translated_address_bits (void);
+
+/* Get the current mask for address bits used in address translation.  */
+extern uintptr_t __libc_get_translated_address_mask (void);
+
+/* Return the tagged address of __ADDR with the tag value __TAG.  */
+extern void *__libc_tag_address (void *__addr, unsigned int __tag);
+
+/* Return the untagged address of __ADDR.  */
+extern void *__libc_untag_address (void *__addr);
+
+#else
+# include <inline-tagged-address.h>
+#endif
diff --git a/manual/Makefile b/manual/Makefile
index e83444341e..08df2daa6b 100644
--- a/manual/Makefile
+++ b/manual/Makefile
@@ -34,7 +34,8 @@  info: $(objpfx)libc.info
 endif
 
 chapters = $(addsuffix .texi, \
-		       intro errno memory ctype string charset locale	\
+		       intro errno memory tagged-address ctype string	\
+		       charset locale					\
 		       message search pattern io stdio llio filesys	\
 		       pipe socket terminal syslog math arith time	\
 		       resource setjmp signal startup process ipc job	\
diff --git a/manual/ctype.texi b/manual/ctype.texi
index d0618c5c38..28af73ff0e 100644
--- a/manual/ctype.texi
+++ b/manual/ctype.texi
@@ -1,4 +1,4 @@ 
-@node Character Handling, String and Array Utilities, Memory, Top
+@node Character Handling, String and Array Utilities, Tagged Address, Top
 @c %MENU% Character testing and conversion functions
 @chapter Character Handling
 
diff --git a/manual/memory.texi b/manual/memory.texi
index 0b2b9c8795..2e283e41f9 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -1,4 +1,4 @@ 
-@node Memory, Character Handling, Error Reporting, Top
+@node Memory, Tagged Address, Error Reporting, Top
 @chapter Virtual Memory Allocation And Paging
 @c %MENU% Allocating virtual memory and controlling paging
 @cindex memory allocation
diff --git a/manual/tagged-address.texi b/manual/tagged-address.texi
new file mode 100644
index 0000000000..d10e67b7e2
--- /dev/null
+++ b/manual/tagged-address.texi
@@ -0,0 +1,48 @@ 
+@node Tagged Address, Character Handling, Memory, Top
+@c %MENU% Tagged address functions and macros
+@chapter Tagged Address
+
+By default, the number of the address bits used in address translation
+is the number of address bits.  But it can be changed by ARM Top-byte
+Ignore (TBI) or Intel Linear Address Masking (LAM).
+
+@Theglibc{} provides one function and two macros in the header file
+@file{sys/tagged-address.h} to manipulate translated address bits,
+which is the number of the address bits used in address translation,
+with restrictions:
+
+@itemize @bullet
+@item
+All bits between 0 and N - 1, where N is the number of translated address
+bits, are used in address translation.
+
+@item
+All pointers participating in a pointer arithmetic operation should have
+the same tag if they point to the same memory object so that pointer
+equality operation can be performed on tagged pointers.
+@end itemize
+
+@pindex sys/tagged-address.h
+
+@deftypefun int set_translated_address_mask (uintptr_t @var{mask})
+@standards{GNU, sys/tagged-address.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+Set the mask for address bits used in address translation to @var{mask}.
+Only bits set in @var{mask} will be used in address translation.  The
+return value is @code{0} on success and @code{-1} on failure.  This
+function can be called only once before @code{main} and thread creation.
+The possible @code{errno} error conditions are @code{ENODEV}, @code{EPERM},
+@code{EINVAL}, and @code{ENOSYS}.
+@end deftypefun
+
+@deftypefn Macro int TRANSLATED_ADDRESS_VALID_BITS (@var{bits})
+This macro returns a nonzero value (true) if @var{bits} is a valid
+constant number of the lower address bits which can be used in address
+translation.
+@end deftypefn
+
+@deftypefn Macro {const uintptr_t} TRANSLATED_ADDRESS_MASK (@var{bits})
+This macro returns a nonzero value which can be passed to
+@code{set_translated_address_mask} to specify the lower address
+@var{bits} for address translation.
+@end deftypefn
diff --git a/misc/Makefile b/misc/Makefile
index 1083ba3bfc..bada0cfcc2 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -38,7 +38,10 @@  headers	:= sys/uio.h bits/uio-ext.h bits/uio_lim.h \
 	   bits/select2.h bits/hwcap.h sys/auxv.h \
 	   sys/sysmacros.h bits/sysmacros.h bits/types/struct_iovec.h \
 	   bits/err-ldbl.h bits/error-ldbl.h \
-	   sys/single_threaded.h
+	   sys/single_threaded.h \
+	   sys/tagged-address.h \
+	   bits/tagged-address-mask.h \
+	   bits/tagged-address-valid-bits.h
 
 routines := brk sbrk sstk ioctl \
 	    readv writev preadv preadv64 pwritev pwritev64 \
@@ -73,7 +76,8 @@  routines := brk sbrk sstk ioctl \
 	    fgetxattr flistxattr fremovexattr fsetxattr getxattr \
 	    listxattr lgetxattr llistxattr lremovexattr lsetxattr \
 	    removexattr setxattr getauxval ifunc-impl-list makedev \
-	    allocate_once fd_to_filename single_threaded unwind-link
+	    allocate_once fd_to_filename single_threaded unwind-link \
+	    tagged-address set-translated-address-mask
 
 generated += tst-error1.mtrace tst-error1-mem.out \
   tst-allocate_once.mtrace tst-allocate_once-mem.out
@@ -89,7 +93,11 @@  tests := tst-dirname tst-tsearch tst-fdset tst-mntent tst-hsearch \
 	 tst-preadvwritev2 tst-preadvwritev64v2 tst-warn-wide \
 	 tst-ldbl-warn tst-ldbl-error tst-dbl-efgcvt tst-ldbl-efgcvt \
 	 tst-mntent-autofs tst-syscalls tst-mntent-escape tst-select \
-	 tst-ioctl
+	 tst-ioctl \
+	 tst-tagged-address-1 tst-tagged-address-1-static \
+	 tst-tagged-address-2 tst-tagged-address-2-static \
+	 tst-tagged-address-3 tst-tagged-address-3-static \
+	 tst-tagged-address-4 tst-tagged-address-4-static
 
 tests-time64 := \
   tst-select-time64 \
@@ -99,11 +107,24 @@  tests-time64 := \
 
 # Tests which need libdl.
 ifeq (yes,$(build-shared))
-tests += tst-gethostid
+tests += tst-gethostid \
+  tst-tagged-address-5 \
+  tst-tagged-address-6 \
+  tst-tagged-address-7
+modules-names-tst-tagged-address = \
+  tst-tagged-address-mod-5 \
+  tst-tagged-address-mod-6 \
+  tst-tagged-address-mod-7
+modules-names += $(modules-names-tst-tagged-address)
+modules-names-tests += $(modules-names-tst-tagged-address)
 endif
 
 tests-internal := tst-atomic tst-atomic-long tst-allocate_once
-tests-static := tst-empty
+tests-static := tst-empty \
+  tst-tagged-address-1-static \
+  tst-tagged-address-2-static \
+  tst-tagged-address-3-static \
+  tst-tagged-address-4-static
 
 # Test for the internal, non-exported __fd_to_filename function.
 tests-internal += tst-fd_to_filename
@@ -172,3 +193,12 @@  $(objpfx)tst-select: $(librt)
 $(objpfx)tst-select-time64: $(librt)
 $(objpfx)tst-pselect: $(librt)
 $(objpfx)tst-pselect-time64: $(librt)
+
+$(objpfx)tst-tagged-address-2: $(shared-thread-library)
+$(objpfx)tst-tagged-address-2-static: $(static-thread-library)
+$(objpfx)tst-tagged-address-5: $(objpfx)tst-tagged-address-mod-5.so
+$(objpfx)tst-tagged-address-mod-5.so: $(libsupport)
+$(objpfx)tst-tagged-address-6: $(objpfx)tst-tagged-address-mod-6.so
+$(objpfx)tst-tagged-address-mod-6.so: $(libsupport)
+$(objpfx)tst-tagged-address-7.out: $(objpfx)tst-tagged-address-mod-7.so
+$(objpfx)tst-tagged-address-mod-7.so: $(libsupport)
diff --git a/misc/Versions b/misc/Versions
index d5b348e83a..fb102ca2b3 100644
--- a/misc/Versions
+++ b/misc/Versions
@@ -164,6 +164,10 @@  libc {
   GLIBC_2.32 {
     __libc_single_threaded;
   }
+  GLIBC_2.35 {
+    # Support tagged address.
+    set_translated_address_mask;
+  }
   GLIBC_PRIVATE {
     __madvise;
     __mktemp;
@@ -173,5 +177,11 @@  libc {
     __sched_get_priority_min; __sched_get_priority_max;
     __libc_allocate_once_slow;
     __libc_unwind_link_get;
+
+    # Support tagged address.
+    __libc_get_translated_address_bits;
+    __libc_get_translated_address_mask;
+    __libc_tag_address;
+    __libc_untag_address;
   }
 }
diff --git a/misc/set-translated-address-mask.c b/misc/set-translated-address-mask.c
new file mode 100644
index 0000000000..9a0f6a11cf
--- /dev/null
+++ b/misc/set-translated-address-mask.c
@@ -0,0 +1,41 @@ 
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+#include <ldsodefs.h>
+
+/* Set the mask for address bits used in address translation.  Return 0
+   on success.  Return -1 on error.  */
+
+int
+set_translated_address_mask (uintptr_t mask)
+{
+  if (GL(dl_translated_address_mask_locked) != 0)
+    __set_errno (EPERM);
+  else
+    {
+      /* set_translated_address_mask can only be called once.  */
+      GL(dl_translated_address_mask_locked) = 1;
+
+      /* Only NOP is allowed.  */
+      if (mask == __get_translated_address_mask ())
+	return 0;
+
+      __set_errno (ENOSYS);
+    }
+  return -1;
+}
diff --git a/misc/sys/tagged-address.h b/misc/sys/tagged-address.h
new file mode 100644
index 0000000000..a0a91bad75
--- /dev/null
+++ b/misc/sys/tagged-address.h
@@ -0,0 +1,33 @@ 
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SYS_TAGGED_ADDRESS_H
+#define _SYS_TAGGED_ADDRESS_H 1
+
+#include <features.h>
+#include <stdint.h>
+#include <bits/tagged-address-mask.h>
+
+__BEGIN_DECLS
+
+/* Set the mask for address bits used in address translation.  Return 0
+   on success.  Return -1 on error.  */
+extern int set_translated_address_mask (uintptr_t __mask);
+
+__END_DECLS
+
+#endif /* <sys/tagged-address.h> */
diff --git a/misc/tagged-address.c b/misc/tagged-address.c
new file mode 100644
index 0000000000..02d4123c5c
--- /dev/null
+++ b/misc/tagged-address.c
@@ -0,0 +1,50 @@ 
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+
+/* Get the current address bits used in address translation.  */
+
+unsigned int
+__libc_get_translated_address_bits (void)
+{
+  return __get_translated_address_bits ();
+}
+
+/* Get the current mask for address bits used in address translation.  */
+
+uintptr_t
+__libc_get_translated_address_mask (void)
+{
+  return __get_translated_address_mask ();
+}
+
+/* Return the tagged address of ADDR with the tag value TAG.  */
+
+void *
+__libc_tag_address (void *addr, unsigned int tag)
+{
+  return __tag_address (addr, tag);
+}
+
+/* Return the untagged address of ADDR.  */
+
+void *
+__libc_untag_address (void *addr)
+{
+  return __untag_address (addr);
+}
diff --git a/misc/tst-tagged-address-1-static.c b/misc/tst-tagged-address-1-static.c
new file mode 100644
index 0000000000..3ed71a66c2
--- /dev/null
+++ b/misc/tst-tagged-address-1-static.c
@@ -0,0 +1 @@ 
+#include <tst-tagged-address-1.c>
diff --git a/misc/tst-tagged-address-1.c b/misc/tst-tagged-address-1.c
new file mode 100644
index 0000000000..0751be9b24
--- /dev/null
+++ b/misc/tst-tagged-address-1.c
@@ -0,0 +1,55 @@ 
+/* Tests for set_translated_address_mask before main.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static void
+init_0 (void)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      != 0)
+    FAIL_EXIT1 ("set_translated_address_mask failed: %m");
+}
+
+static void
+init_1 (void)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      == 0)
+    FAIL_EXIT1 ("set_translated_address_mask should fail");
+
+  if (errno != EPERM)
+    FAIL_EXIT1 ("set_translated_address_mask: errno (%m) != EPERM");
+}
+
+static void (*init_array []) (void)
+  __attribute__ ((used, section (".init_array"), aligned (sizeof (void *)))) =
+{
+  &init_0,
+  &init_1
+};
+
+static int
+do_test (void)
+{
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-2-static.c b/misc/tst-tagged-address-2-static.c
new file mode 100644
index 0000000000..ac0d95e6c0
--- /dev/null
+++ b/misc/tst-tagged-address-2-static.c
@@ -0,0 +1 @@ 
+#include <tst-tagged-address-2.c>
diff --git a/misc/tst-tagged-address-2.c b/misc/tst-tagged-address-2.c
new file mode 100644
index 0000000000..00a97148f8
--- /dev/null
+++ b/misc/tst-tagged-address-2.c
@@ -0,0 +1,45 @@ 
+/* Test for set_translated_address_mask before main with pthread.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/tagged-address.h>
+#include <support/xthread.h>
+#include <support/check.h>
+
+static void *
+tf (void *arg)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      == 0)
+    FAIL_EXIT1 ("set_translated_address_mask should fail");
+
+  if (errno != EPERM)
+    FAIL_EXIT1 ("set_translated_address_mask: errno (%m) != EPERM");
+
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  pthread_t thr = xpthread_create (NULL, tf, NULL);
+  xpthread_join (thr);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-3-static.c b/misc/tst-tagged-address-3-static.c
new file mode 100644
index 0000000000..1e3591e0d6
--- /dev/null
+++ b/misc/tst-tagged-address-3-static.c
@@ -0,0 +1 @@ 
+#include <tst-tagged-address-3.c>
diff --git a/misc/tst-tagged-address-3.c b/misc/tst-tagged-address-3.c
new file mode 100644
index 0000000000..04d2f8d3da
--- /dev/null
+++ b/misc/tst-tagged-address-3.c
@@ -0,0 +1,48 @@ 
+/* Tests for set_translated_address_mask to turn off tagged address.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static void
+init (void)
+{
+  uintptr_t mask = (uintptr_t) -1;
+  if (set_translated_address_mask (mask) != 0)
+    FAIL_EXIT1 ("set_translated_address_mask failed: %m");
+}
+
+static void (*init_array []) (void)
+  __attribute__ ((used, section (".init_array"), aligned (sizeof (void *)))) =
+{
+  &init
+};
+
+static int
+do_test (void)
+{
+  uintptr_t mask = (uintptr_t) -1;
+  uintptr_t curent_mask = __libc_get_translated_address_mask ();
+  if (curent_mask != mask)
+    FAIL_EXIT1 ("get_translated_address_mask failed: %p != %p",
+		(void *) curent_mask, (void *) mask);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-4-static.c b/misc/tst-tagged-address-4-static.c
new file mode 100644
index 0000000000..b0681f6f9b
--- /dev/null
+++ b/misc/tst-tagged-address-4-static.c
@@ -0,0 +1 @@ 
+#include <tst-tagged-address-4.c>
diff --git a/misc/tst-tagged-address-4.c b/misc/tst-tagged-address-4.c
new file mode 100644
index 0000000000..9131373ba1
--- /dev/null
+++ b/misc/tst-tagged-address-4.c
@@ -0,0 +1,36 @@ 
+/* Test for set_translated_address_mask after main.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      == 0)
+    FAIL_EXIT1 ("set_translated_address_mask should fail");
+
+  if (errno != EPERM)
+    FAIL_EXIT1 ("set_translated_address_mask: errno (%m) != EPERM");
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-5.c b/misc/tst-tagged-address-5.c
new file mode 100644
index 0000000000..f3c6ce5935
--- /dev/null
+++ b/misc/tst-tagged-address-5.c
@@ -0,0 +1,25 @@ 
+/* Tests for set_translated_address_mask in a shared library before main.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+static int
+do_test (void)
+{
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-6.c b/misc/tst-tagged-address-6.c
new file mode 100644
index 0000000000..60c6497af2
--- /dev/null
+++ b/misc/tst-tagged-address-6.c
@@ -0,0 +1,34 @@ 
+/* Tests for set_translated_address_mask to turn off tagged address.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  uintptr_t mask = (uintptr_t) -1;
+  uintptr_t curent_mask = __libc_get_translated_address_mask ();
+  if (curent_mask != mask)
+    FAIL_EXIT1 ("get_translated_address_mask failed: %p != %p",
+		(void *) curent_mask, (void *) mask);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-7.c b/misc/tst-tagged-address-7.c
new file mode 100644
index 0000000000..7d987e19e3
--- /dev/null
+++ b/misc/tst-tagged-address-7.c
@@ -0,0 +1,41 @@ 
+/* Test for set_translated_address_mask in a dlopened shared library
+   after main.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stddef.h>
+#include <dlfcn.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  const char *modname = "$ORIGIN/tst-tagged-address-mod-7.so";
+  void *h = dlopen (modname, RTLD_LAZY);
+
+  if (h == NULL)
+    {
+      const char *err = dlerror ();
+      FAIL_EXIT1 ("cannot open '%s': %s\n", modname, err);
+    }
+
+  dlclose (h);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-tagged-address-mod-5.c b/misc/tst-tagged-address-mod-5.c
new file mode 100644
index 0000000000..88b8d6a261
--- /dev/null
+++ b/misc/tst-tagged-address-mod-5.c
@@ -0,0 +1,47 @@ 
+/* Tests for set_translated_address_mask in a shared library.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static void
+init_0 (void)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      != 0)
+    FAIL_EXIT1 ("set_translated_address_mask failed: %m");
+}
+
+static void
+init_1 (void)
+{
+  if (set_translated_address_mask (__libc_get_translated_address_mask ())
+      == 0)
+    FAIL_EXIT1 ("set_translated_address_mask should fail");
+
+  if (errno != EPERM)
+    FAIL_EXIT1 ("set_translated_address_mask: errno (%m) != EPERM");
+}
+
+static void (*init_array []) (void)
+  __attribute__ ((used, section (".init_array"), aligned (sizeof (void *)))) =
+{
+  &init_0,
+  &init_1
+};
diff --git a/misc/tst-tagged-address-mod-6.c b/misc/tst-tagged-address-mod-6.c
new file mode 100644
index 0000000000..4d9396425d
--- /dev/null
+++ b/misc/tst-tagged-address-mod-6.c
@@ -0,0 +1,34 @@ 
+/* Tests for set_translated_address_mask to turn off tagged address.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static void
+init (void)
+{
+  uintptr_t mask = (uintptr_t) -1;
+  if (set_translated_address_mask (mask) != 0)
+    FAIL_EXIT1 ("set_translated_address_mask failed: %m");
+}
+
+static void (*init_array []) (void)
+  __attribute__ ((used, section (".init_array"), aligned (sizeof (void *)))) =
+{
+  &init
+};
diff --git a/misc/tst-tagged-address-mod-7.c b/misc/tst-tagged-address-mod-7.c
new file mode 100644
index 0000000000..7d8f80a232
--- /dev/null
+++ b/misc/tst-tagged-address-mod-7.c
@@ -0,0 +1,35 @@ 
+/* Tests for set_translated_address_mask to turn off tagged address in
+   a shared library.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/tagged-address.h>
+#include <support/check.h>
+
+static void
+init (void)
+{
+  uintptr_t mask = (uintptr_t) -1;
+  if (set_translated_address_mask (mask) == 0)
+    FAIL_EXIT1 ("set_translated_address_mask should have failed");
+}
+
+static void (*init_array []) (void)
+  __attribute__ ((used, section (".init_array"), aligned (sizeof (void *)))) =
+{
+  &init
+};
diff --git a/sysdeps/generic/inline-tagged-address.h b/sysdeps/generic/inline-tagged-address.h
new file mode 100644
index 0000000000..9fb8eb7ecf
--- /dev/null
+++ b/sysdeps/generic/inline-tagged-address.h
@@ -0,0 +1,43 @@ 
+/* Inline tagged address functions.  Generic version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+
+static inline unsigned int
+__get_translated_address_bits (void)
+{
+  return sizeof (uintptr_t) * 8;
+}
+
+static inline uintptr_t
+__get_translated_address_mask (void)
+{
+  return (uintptr_t) -1;
+}
+
+static inline void *
+__tag_address (void *addr, unsigned int tag)
+{
+  return addr;
+}
+
+static inline void *
+__untag_address (void *addr)
+{
+  return addr;
+}
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 9c15259236..a77a52567f 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -489,6 +489,10 @@  struct rtld_global
 #else
   EXTERN int _dl_thread_gscope_count;
 #endif
+
+  /* If nonzero, the mask for address bits used in address translation
+     is locked.  */
+  EXTERN int _dl_translated_address_mask_locked;
 #ifdef SHARED
 };
 # define __rtld_global_attribute__
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 2e7603d9ed..0f314eec3e 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2780,6 +2780,7 @@  GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
 GLIBC_2.34 tss_set F
+GLIBC_2.35 set_translated_address_mask F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 095e914b73..7106aac0ad 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2521,6 +2521,7 @@  GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
 GLIBC_2.34 tss_set F
+GLIBC_2.35 set_translated_address_mask F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index dd910f7fe9..00ff5571be 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2627,3 +2627,4 @@  GLIBC_2.34 tss_create F
 GLIBC_2.34 tss_delete F
 GLIBC_2.34 tss_get F
 GLIBC_2.34 tss_set F
+GLIBC_2.35 set_translated_address_mask F